The research proposed in this project involves three primary factors. The majority of this grant will be devoted to ascertaining the relative reinforcing efficacy of psychomotor stimulants. The subjects are rhesus monkeys which have been conditioned to intravenously self- administer these substances. Three operant paradigms will be used in an attempt to realize this goal. These procedures include (1) a progressive ratio schedule of reinforcement; (2) a conditioned reinforcement paradigm, and (3) a punishment paradigm. The effects of these substances on shock suppressed behavior (punished responding) will also ascertained. Secondly, studies will be undertaken in this research program to determine the ability of substances, e.g., atropine, chlorpromazine, to specifically antagonize the reinforcing action of psychomotor stimulants as opposed to their ability to modify stimulant self-administration behavior via other mechanisms. Lastly, the effect of varying the duration of access and the duration of the interaccess period on the pattern and rate of responding for intravenously self- administered psychomotor stimulants will also be analyzed.